Non mutating algorithms: std::find

• Does not modify the contents of the container they work on.
• Typical operation is searching the container for a particular element and returning its position

template <class InputIter, Class T>
InputIter find(InputIter b, InputIter e, const T &t);

• This returns an iterator to the first matching element (or end() if not found), so checking against the end is crucial for sanity.

template <class InputIter, Class Predicate>
InputIter find(InputIter b, InputIter e, Predicate p);

• Finds position of first element that makes Predicate true in range b to e, otherwise position e is returned.

Another possibility:

template <class InputIter, Class Function>
void for_each(InputIter b, InputIter e, Function f);

• Apply f for each value found in range b to e.
• std::for_each is great for side effects, but in modern C++, it's usually replaced with range-based for loops or algorithms like std::transform or std::accumulate for actual data transformation.

find() algorithm example

#include <algorithm>
#include <iostream>
#include <ostream>
#include <string>

int main() {
  std::string words[5] = {"my", "hop", "mop", "hope", "cope"};
  std::string *where;

  where = std::find(words, words + 5, "hop");
  std::cout << *++where << "\n";
  std::sort(words, words + 5);
  where = std::find(words, words + 5, "hop");
  std::cout << *++where << "\n";
}

Expected output:

mop
hope

• Here, sort does a lexicographic sort. "cope" will end up first and "my" will end up last.